I present you a review of HFW-1831E camera. This is a h265 Lite series model, most likely equipped with fairly new IMX334 Sony sensor. This is a 1/1.8 inch, 8 megapixel CMOS with a pixel size of 2 micrometers. I got a model with 4mm lens, giving a horizontal FOV of around 87 degrees. I will oppose it to 5831R-ZE model, which is equipped with IMX274 CMOS (1/2.5 inch, 8MP) and also 4231EM-AS Stalight camera, equipped with very popular IMX290 fullHD sensor. I got the camera from Andy in exchange for a in-depth review. Thank you Andy 
Before I start the review, I would like to mention a few things. For this review I decided to relay both on video examples with some motion, as well as snaps from recorded clips. Previous reviews were based mostly on static snaps from cameras, but as some users noticed, the real quality of the image is when some motion appears. Also I changed a method of taking stills. Previously these were mostly snapshots from Web Interface. I've noticed however, that this function severely reduces amount of data in the picture. It cuts off shadows and highlights. See an example below.
On the left is a bitmap file taken as snapshot with Web Interface function. On the right is a paused h264 movie of the same scene. At first glance not a big difference. But when I squeeze the histogram (brighten the image) it turns out, the left image has no data in the background grass part. The same goes for highlights. I've already mentioned this in HDW5831R-ZE review. Most of WDR data might be lost, when using snapshot button in Web Interface. So be careful when using it, especially in vulnerable situations, when every detail of the image is necessary, for recognition. In this review as well as HFW4239T review, I used only frames grabbed straight from DAV files.
The movie files in this review were also untouched during montage. I used DAV files, converted to AVI (no recompression) and then converted to mp4 (also no recompression). The only additional compression you see is introduced by Youtube (please, watch all Youtube material in 4K resolution!). All this, together with a few other obstacles I encountered during testing, made me testing this camera for over a month. Sorry for such delay.
The first thing to note, is that this model is very compact. It is way smaller than 4239T. Build quality is good. The only plastic part is top and bottom white cover. All the rest seems to be metal. A very important difference between this model and its varifocal brother, is that it has NO SD CARD SLOT. I wasn’t aware of it. Before I checked the specs, I was searching a place to disassemble the camera and put an SD card in. It took me at least 10 minutes to realize that something is wrong Here is a link to a Thread where Burton_Flooring shows how to disassemble it.
The camera ISO ranges from around 50 to 10000.
Top gain is 1EV lower than most of the other cams I’ve tested. There is however a fairly bright lens onboard with f1.6 aperture, so final brightness scale from 0% to 100% gain should be almost identical to HDW4231EM-AS. In comparison to 5831R-ZE the starting gain will be 1EV brighter, while top gain will be 1EV lower.
Because of significantly larger pixel size in comparison to 5831R-ZE – 2.0um vs 1.62um - we should expect a better image quality from this camera. The recorded material will be also more fluent, because it supports 25fps (also in WDR mode) while 5831R-ZE supports only 15fps (14fps in WDR mode). I wasn’t expecting any difference during daylight but it turned out that the image is slightly sharper. It’s actually sharp from edge to edge, while with 5831 I have a problem with out-of-focus areas of the image at certain zoom positions. I’ve mentioned this in its review. To compare both cams I’ve set 5831 zoom to match FOV of 1831. Unfortunately at this position there is blurriness in top-right corner. So when comparing both cams, please do not take this part of the image as representative of camera resolution.
Studying carefully the image I’ve noticed that despite it is very sharp, there is some kind of softness creeping in. It looks like the color (chroma) is slightly soft in comparison to objects outlines (luma). It resembles a leaking color out of object. This can be a 4:2:0 chroma subsampling issue here, but I’m only guessing. https://en.wikipedia.org/wiki/Chroma_subsampling This is mostly visible when motion appears. Object's edges become soft.
It might sound strange, but the codec efficiency seems to be worse in comparison to 5831. In shadowed areas and on moving objects, blocky artifacts appear. Luckily Dahua has raised the top bitrate in 1831 to over 15mbit/s. At 25fps this is an equivalent for 9mbit/s @ 15fps in 5831. Before firmware update I had an option to set over 50mbit/s in custom mode. However at 30mbit/s I had lot of dropped frames even in live view. Over 40mbit/s there was no image, only black window. After rising the bitrate to 15000kbps the blocky shadows are much reduced but still present. Even 30mbit/s do not resolve the problem, while 5831R-ZE is almost free of such artifacts at 9mbit/s. See the below example.
Checkout motorcycle detail:
On 5831 turning smart codec on, makes a significant improvement over image. There is no pulsation of I-frames and overall quality is improved. On 1831 the difference is minor. I can still notice pulsation of I-frames and some blocks of compression on moving objects. Only after reducing resolution to 4MP while keeping 15mbit/s bitrate, the blocks of compression are mostly gone.
One way to reduce compression blocks in dark areas of the image is to turn on WDR. This will brighten dark parts and give a codec a chance to encode in more efficient way. The WDR on 1831 works much different than on other cameras I’ve tested. It has only 2 modes through the scale. From 1% to 44% it affects the brightness curve. It brightens shadows and reduces highlights without introducing WDR artifacts. It is based on single exposure and I have to admit, it looks very good. From 45% to 100% it turns on true WDR. In this mode the camera favors shadows rather than highlights. Midtones become over-sharpened, shadows are boosted up so much, that there is virtually no place to hide. It much resembles, what in AXIS cameras is called “forensic WDR”.
From a security point of view is seems to be perfect. From esthetic side it is slightly distracting. I much prefer the first WDR mode. At night WDR works well. It does not darken the image as in case of 5831 but introduces noise in shadows. The best setting I found for night is to set WDR for 20% and bring gamma all the way down. This will bring shadows up, but keep noise at acceptable level. Here is an example with such settings for 1/25s exposure:
There is also a downside of true WDR mode. Can you see my face in the video example? It’s completely flat in true WDR mode. Notice also the quality of a text on my t-shirt.
I think, there is no need for commenting nighttime footage. The 1831’s image is better. The noise pattern is a pleasant grain instead of blocks and specks as in 5831. Even at 100% gain, the image is acceptable. Noise reduction should be more efficient on 1831 as it has more frames to stack in a given period of time, due to higher framerate.
When opposed to 4231EM-AS the 1831 gives similar if not slightly better results at night.
Noise reduction seems more aggressive on 1831. Even during daytime - see the stacking artifacts on the car:
It seems to be most flare resistant of all cams I own. See the WDR comparison between 1831 and 5831. The sun makes 5831's image washed out in corners. This might be due to the fact 1831 is a fixed lens camera with less glass through the lens. The varifocal version might introduce more flares.
At daytime the 1831 is a definite winner. The only drawback is its compression. 4231EM-AS has a very clean, blockless image, while 1831 despite the 15000kbps and smart codec is still introducing lot of compression artifacts. Especially when objects are moving fast.
The scaling algorithm of the image has been vastly improved on 1831. Now it works exactly how it should. 2655x1520 / 1920x1080 / 1280x720 resolutions are full of detail and introduce less noise. FullHD image at night looks very good.
Overall, in terms of image quality, this camera is my favorite. Not only you get a sharp, clear image at daytime, but also a decent image quality at night, even in color. There are almost no flares at night. 25fps gives you a pleasant, fluent video both for WDR and nonWDR mode. Scaling to lower resolutions works like charm now. You also get higher than on other cams bitrate option. WDR curves correction boosts the image without introducing any artifacts.
From the drawback list I can point out a less efficient compression algorithm, which introduces blocks of compression on moving objects. The smart codec slightly improves this situation, but 5831 seems more efficient here. There is a problem with resetting date stamp. Even after firmware update. This model has no SD card slot. For me that's the worst thing, as I have no NVR and rely only on SD cards. Its varifocal brother has a SD slot.
Before I start the review, I would like to mention a few things. For this review I decided to relay both on video examples with some motion, as well as snaps from recorded clips. Previous reviews were based mostly on static snaps from cameras, but as some users noticed, the real quality of the image is when some motion appears. Also I changed a method of taking stills. Previously these were mostly snapshots from Web Interface. I've noticed however, that this function severely reduces amount of data in the picture. It cuts off shadows and highlights. See an example below.
On the left is a bitmap file taken as snapshot with Web Interface function. On the right is a paused h264 movie of the same scene. At first glance not a big difference. But when I squeeze the histogram (brighten the image) it turns out, the left image has no data in the background grass part. The same goes for highlights. I've already mentioned this in HDW5831R-ZE review. Most of WDR data might be lost, when using snapshot button in Web Interface. So be careful when using it, especially in vulnerable situations, when every detail of the image is necessary, for recognition. In this review as well as HFW4239T review, I used only frames grabbed straight from DAV files.
The movie files in this review were also untouched during montage. I used DAV files, converted to AVI (no recompression) and then converted to mp4 (also no recompression). The only additional compression you see is introduced by Youtube (please, watch all Youtube material in 4K resolution!). All this, together with a few other obstacles I encountered during testing, made me testing this camera for over a month. Sorry for such delay.
The first thing to note, is that this model is very compact. It is way smaller than 4239T. Build quality is good. The only plastic part is top and bottom white cover. All the rest seems to be metal. A very important difference between this model and its varifocal brother, is that it has NO SD CARD SLOT. I wasn’t aware of it. Before I checked the specs, I was searching a place to disassemble the camera and put an SD card in. It took me at least 10 minutes to realize that something is wrong
Here is a link to a Thread where Burton_Flooring shows how to disassemble it.The camera ISO ranges from around 50 to 10000.
Top gain is 1EV lower than most of the other cams I’ve tested. There is however a fairly bright lens onboard with f1.6 aperture, so final brightness scale from 0% to 100% gain should be almost identical to HDW4231EM-AS. In comparison to 5831R-ZE the starting gain will be 1EV brighter, while top gain will be 1EV lower.
Because of significantly larger pixel size in comparison to 5831R-ZE – 2.0um vs 1.62um - we should expect a better image quality from this camera. The recorded material will be also more fluent, because it supports 25fps (also in WDR mode) while 5831R-ZE supports only 15fps (14fps in WDR mode). I wasn’t expecting any difference during daylight but it turned out that the image is slightly sharper. It’s actually sharp from edge to edge, while with 5831 I have a problem with out-of-focus areas of the image at certain zoom positions. I’ve mentioned this in its review. To compare both cams I’ve set 5831 zoom to match FOV of 1831. Unfortunately at this position there is blurriness in top-right corner. So when comparing both cams, please do not take this part of the image as representative of camera resolution.
Studying carefully the image I’ve noticed that despite it is very sharp, there is some kind of softness creeping in. It looks like the color (chroma) is slightly soft in comparison to objects outlines (luma). It resembles a leaking color out of object. This can be a 4:2:0 chroma subsampling issue here, but I’m only guessing. https://en.wikipedia.org/wiki/Chroma_subsampling This is mostly visible when motion appears. Object's edges become soft.
It might sound strange, but the codec efficiency seems to be worse in comparison to 5831. In shadowed areas and on moving objects, blocky artifacts appear. Luckily Dahua has raised the top bitrate in 1831 to over 15mbit/s. At 25fps this is an equivalent for 9mbit/s @ 15fps in 5831. Before firmware update I had an option to set over 50mbit/s in custom mode. However at 30mbit/s I had lot of dropped frames even in live view. Over 40mbit/s there was no image, only black window. After rising the bitrate to 15000kbps the blocky shadows are much reduced but still present. Even 30mbit/s do not resolve the problem, while 5831R-ZE is almost free of such artifacts at 9mbit/s. See the below example.
Checkout motorcycle detail:
On 5831 turning smart codec on, makes a significant improvement over image. There is no pulsation of I-frames and overall quality is improved. On 1831 the difference is minor. I can still notice pulsation of I-frames and some blocks of compression on moving objects. Only after reducing resolution to 4MP while keeping 15mbit/s bitrate, the blocks of compression are mostly gone.
One way to reduce compression blocks in dark areas of the image is to turn on WDR. This will brighten dark parts and give a codec a chance to encode in more efficient way. The WDR on 1831 works much different than on other cameras I’ve tested. It has only 2 modes through the scale. From 1% to 44% it affects the brightness curve. It brightens shadows and reduces highlights without introducing WDR artifacts. It is based on single exposure and I have to admit, it looks very good. From 45% to 100% it turns on true WDR. In this mode the camera favors shadows rather than highlights. Midtones become over-sharpened, shadows are boosted up so much, that there is virtually no place to hide. It much resembles, what in AXIS cameras is called “forensic WDR”.
From a security point of view is seems to be perfect. From esthetic side it is slightly distracting. I much prefer the first WDR mode. At night WDR works well. It does not darken the image as in case of 5831 but introduces noise in shadows. The best setting I found for night is to set WDR for 20% and bring gamma all the way down. This will bring shadows up, but keep noise at acceptable level. Here is an example with such settings for 1/25s exposure:
There is also a downside of true WDR mode. Can you see my face in the video example? It’s completely flat in true WDR mode. Notice also the quality of a text on my t-shirt.
I think, there is no need for commenting nighttime footage. The 1831’s image is better. The noise pattern is a pleasant grain instead of blocks and specks as in 5831. Even at 100% gain, the image is acceptable. Noise reduction should be more efficient on 1831 as it has more frames to stack in a given period of time, due to higher framerate.
When opposed to 4231EM-AS the 1831 gives similar if not slightly better results at night.
Noise reduction seems more aggressive on 1831. Even during daytime - see the stacking artifacts on the car:
It seems to be most flare resistant of all cams I own. See the WDR comparison between 1831 and 5831. The sun makes 5831's image washed out in corners. This might be due to the fact 1831 is a fixed lens camera with less glass through the lens. The varifocal version might introduce more flares.
At daytime the 1831 is a definite winner. The only drawback is its compression. 4231EM-AS has a very clean, blockless image, while 1831 despite the 15000kbps and smart codec is still introducing lot of compression artifacts. Especially when objects are moving fast.
The scaling algorithm of the image has been vastly improved on 1831. Now it works exactly how it should. 2655x1520 / 1920x1080 / 1280x720 resolutions are full of detail and introduce less noise. FullHD image at night looks very good.
Overall, in terms of image quality, this camera is my favorite. Not only you get a sharp, clear image at daytime, but also a decent image quality at night, even in color. There are almost no flares at night. 25fps gives you a pleasant, fluent video both for WDR and nonWDR mode. Scaling to lower resolutions works like charm now. You also get higher than on other cams bitrate option. WDR curves correction boosts the image without introducing any artifacts.
From the drawback list I can point out a less efficient compression algorithm, which introduces blocks of compression on moving objects. The smart codec slightly improves this situation, but 5831 seems more efficient here. There is a problem with resetting date stamp. Even after firmware update. This model has no SD card slot. For me that's the worst thing, as I have no NVR and rely only on SD cards. Its varifocal brother has a SD slot.
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